Chain



July 15, 194 A. E. FO'CKE ET AL CHAIN Filed July 26, 1940 n r "IIIII'INVENTORS. 1 67mm fff'acxs and Patented July 15, 1947 CHAIN Arthur E.Focke and George G. Mize, Indianapolis, Ind., assignors to Diamond Chainand Manufacturing Company, Indianapolis, Ind,

a corporation of Indiana Application July 26, 1940, Serial No. 347,612

25 Claims. 1

Our invention relates to power-transmission chains of the type in whicheach pair of adjacent links are interconnected through the medium of atransversely extending pin press-fitted into pitch holes in laterallyspaced side plates of one link and rotatably received in a transverselyeX- tending opening in the other link. Most commonly, such transverseopenin is the bore of a bushing the ends of which are press-fitted. intopitch holes in the side plates of the associated link; and the chain ismade up of alternating pin-links and bushing-links, each pin-linkembodying two longitudinally spaced pins and each bushing-link embodyingtwo longitudinally spaced bushings. Frequently, sprocket-engagingrollers are rotatably mounted on the chain-bushings; and our inventionwill hereinafter be described as embodied in such a roller chain. It isto be understood, however, that this invention is directed to themounting of the pins in side plates and, in the case of a chainembodying bushings, to the mounting of the bushings in side plates; andthat the invention is applicable to various types of chain having pinsor pins and bushings through the medium of which adjacent chainlinks arepivotally interconnected.

When such chains of the general type just referred to fail in fatigue asthe result of repeated variations in the load to which they aresubjected in use, the failure is almost always a fracture of one or moreof the side plates in the vicinity of one of the pitch holes therein. Itis the primary object of our invention to improve the fatigue resistanceof chains of the type described by increasing materially the maximumload which, when repeatedly applied to the chain, will not result infailure of the side plates.

We have discovered that the resistance of the side plates to fatigue isgreatly affected by the character of the fit of the pins and bushingswithin the pitch holes in the side plates. The smoother and more densethe surfaces of the pitch holes in the side plates and, within limits,the more tightly the pins or bushings fit in those holes, the greaterwill be the fatigue resistance of the chain against failure by fractureof the side plates.

The accompanying drawing illustrates our invention: Fig. 1 is a planview, in partial section, of a roller chain; Figs. 2 and 3 are sectionalviews illustrating two different means by which the surfaces of theholes in each side plate may be improved to enhance fatigue resistance;and Fig, 4 is a section through a side plate finished in the preferredmanner.

The chain shown in Fig. 1 is of the conventional roller type. Itembodies a plurality of sprocketengaging elements interconnected by aseries of pin-links, each of the latter comprising two outer side platesIll and two pins II which extend through alined holes in the ends of theside plates. Each of the sprocket-engaging elements comprises a pair ofspaced inner side plates I5, pinreceiving bushings [6 extending throughholes in the ends of such side plates, and rollers ll rotatably mountedrespectively on such bushings between the side plates I5.

When chains of the type described fail in fatigue the failure is almostalways by fracture of one or more of the side plates [0 and 15, thefracture extending outwardly from one of the pitch holes generallylaterally of the side plate. As indicated above, we have found that theresistance of the side plates to such failure as the result of fatigueis dependent to a great extent upon the fit of the pins and bushingsWithin the pitch holes in the side plates. Specifically, the resistanceof the side plates to failure may be increased by increasing thesmoothness and density of the surfaces of the pitch holes in the sideplates and, within limits, by increasing the tightness of the fit of thepins or bushings within those holes.

It has been customary in chain of the type with which our invention isconcerned to make the pins I l of such a diameter that they will have apress fit in the holes in the side plates I 0. The purpose of this wasto prevent the pins from turning in the side plates and thereby toinsure that any wear resulting from relative angular movement of twoadjacent links of the chain would occur on the interengaging surfaces ofthe pins and bushings, as those surfaces are of considerably largerarea, and therefore subject to a materially smaller unit load, than arethe interengaging surfaces of the pins H and side plates [0.

Since rotative movement and axial movement of a pin H within theassociated side-plate hole both involve friction between the samesurfaces, the firmness with which the pin is held against rotation inthe side plate, as Well as the firmness with which the pin is heldagainst axial movement, may be measured by the force required to expelthe pin from the side plate. To insure prevention of pin movement it hasbeen found that the force required to expel the pin axially from theside plate should vary with the square of the pin-diameter and, inpounds, should be about such as is represented by the expression 10,000D where D is the diameter of the pin in inches. Tolerances now in commonuse by manufacturers of chain are such as will provide, irrespective ofside-plate thickness, pin-expelling forces in the neighborhood of 10,000D pounds when the side plates are not heat-treated. When heat-treatedside plates are employed, the pinexpelling force found in present daycommercial chain may be somewhat higher than 10,000 D pounds.

We have found that the resistance of the outer side plates H! to failurefrom fatigue can be materially increased if such nominal diameters forpins and pin-holes, and such permissible tolerances for thosedimensions, are maintained as will insure minimum pin-expelling forceconsiderably higher than those found in commercial chain as nowgenerally manufactured. In practicing our invention with side plateswhich are not heat treated, we establish nominal diameters andtolerances such that the minimum force required to expel any pin fromits associated side plate will be at least 15,000 D and preferably atleast 20,000 D pounds. When employing heattreated side plates thenominal diameters and tolerances are set so that the minimum forcerequired to expel each pin from its side plate will be at least 20,000 Dpounds, and preferably at least 30,000 D pounds.

The above values for the minimum force required to expel a pin from itsside plate are those suitable for use in practicing our invention whenthe thickness of the side plate is approximately 40% of the pindiameter, which is the proportion obtaining in the vast majority ofroller chains made today. The best results in increased fatigueresistance are secured when the force required to expel a pin increaseswith the sideplate thickness. Taking into account the possibility thatthe relation of side-plate thickness to pin-diameter may vary, thecomplete expression for the minimum force in pounds required to expelpin from an untreated side plate is 37,500 DT (and preferably 50,000 DT)where D is the nominal pin diameter as before, and T is the side-platethickness in inches. For heattreated side plates, the expression wouldbe 50,000 DT, and preferably 75,000 DT.

The increased tightness in the fit of the pins, which results from thepractice of our invention,

introduces into the outer side plates in the regions surrounding thepitch holes initial unit stresses which are materially higher than thoseexisting in chains as now manufactured. We

believe that it is the enhancement of these initial unit stresses whichaccounts for the increased fatigue resistance possessed by chain made inaccordance with our invention.

In the same way that increased initial unit stress in the region of thepin receiving holes promotes increased fatigue resistance of the outerside plates I0, so will increased initial stress in the region of thebushing-receiving holes promote increased fatigue resistance of theinner side plates I5. Present day practice in respect to the tightnes offit of the bushings 16 within the side plates results inbushing-expelling forces in the neighborood of 3000 D pounds when theinner side plates are not heat treated, and of 4,000 D pounds, when theinner side plates are heat treated. If the diameter and tolerances ofthe bushings and of the pitch holes in the inner side plates areestablished to insure materially higher bushing-expelling forcessay of4500 D (and preferably 6000 D pounds for untreated side plates and 6000D (preferably 9000 D pounds for heat-treated side plates-a noticeableincrease in fatigue resistance of the inner side plates will beobtained. Here again, these minima presuppose a fixed relationshipbetween the thickness of the side plate and the diameter of the pitchholes therein, such relationship being that existing in the majority ofroller chan now being manufactured in which the thickness of the innerside plates is approximately 28% of the diameter of thebushing-receiving holes. Taking into account possible variations in thisrelationship, the minimum bushing-expelling force with untreated sideplates should be at least 16,000 DT and preferably 21,000 DT. Withheat-treated side plates, the permissible and preferred forces would be21,000 DT and 32,000 DT, respectively. In these expressions for minimumbushing-expelling forces, D represents bushing diameter and T side-platethickness in inches.

The actual force required to expel any pin or bushing from an associatedside plate will vary not only with dimensions but also to some extentwith the condition of lubrication of the pitch-hole surface and thesurface of the pin or bushing therein. The values above set forth forexpelling forces, both in the case of pins and in the case of bushings,assume that the parts will be in the condition existing after ordinarymanufacturing operations-that the pins, bushings, and side plates willnot have been subjected to any processing designed to render theirsurfaces substantially oil free and, on the other hand, that nolubricant will be employed especially for the purpose of facilitatingthe entry of the pins or bushings into the side plates.

We have also found that the resistance of the side plates to failure infatigue is dependent upon the character of the surfaces of the pitchholes. The smoother these surfaces, and the more dense they are, thegreater will be the resistance to fatigue. Most chain made today, or atleast most chain made in high-quantity production, employs side platesin which the pitch holes have been formed by punching and shaving. Inthe punching operation, the punch employed is appreciably smaller thanthe mating die, to provide the necessary break out; and, as a result, ahole produced by a single punching operation is frusto-conical. Toremove or reduce the taper from punched holes in side plates, they areusually subjected to a shaving operation, in which a punch slightlylarger than the maximum diameter of the original punched hole is forcedthrough the hole to remove a relatively small quantity of metal. Thesurface left by such operations is, for the most part, a fracturesurface, or a surface resulting from a multiplicity of relatively smallfractures; and, as a result, it is relatively rough. Other commonmethods of holesizing, such as reaming and broaching, also involve theremoval of metal and produce surfaces which are relatively rough.

If the irregularities left by the usual methods of finishing the pitchholes are removed and the holes in the side plates given their finalsize by an operation which will produce a smooth, dens-e surface, 'animproved fatigue resistance will result. In order to produce apitch-hole surface of the desired characteristics, we enlarge the pitchholes to their final size by a coldwvorking operation, preferably bydrifting either with a hardened ball 25 as shown in Fig. 2 or with ahardened and tapered drift-pin 26 as shown in Fig. 3. The diameter ofthe ball 25, or the maxi mum diameter of the drift-pin 126, should be afew thousandths of an inch larger than the lar est diameter of the holethrough which the ball or pin is forced.

We find that with the pitch holes drifted to their final diameter,either with a hardened ball or with a hardened drift-pin, the fatigueresistance of the side plates is materially increased even though fit ofthe pins or bushings within those holes is such as will result inexpelling forces approximating those found in standard chain; but inorder to obtain the optimum result from our invention, it is necessarythat the tightness of the fit of the pins and bushings within the sideplates be increased to produce the higher expelling forces above setforth.

Cold-working of the surfaces of the pitch holes, as by drifting, hasseveral eifects which contribute to increasing the fatigue resistance ofthe side plates. In the first place, drifting tends to smooth the holesurface and to eliminate minute cracks which, under repeatedly imposedloads, might develop into fractures. In the second place, driftingeliminates high. spots or projections which, by yielding when the pin orbushing is pressed into the hole, would lessen the stress created in theside plate in the region surrounding the hole. In the third place,cold-working of the metal adjacent the surface of the pitch hole tendsto make that metal more dense, so that when the pin or bushing ispressed into the hole higher unit stresses will result not only in themetal of increased density but also outwardly therebeyond.

We find it desirable to chamfer the edges of the pitch holes at least atthat side of the side plate from which the pin or bushing enters duringassembly of the link. The chamfering of the holeedge is preferablyeffected by cold working, conveniently in the manner indicated in Fig.2. There the drifting ball 25 is shown as being forced through the pitchhole by a punch 3d having above its lower end a shoulder 3 l. The lowerportion of the punch is cylindrical, and, at the point where it joinsthe shoulder 3!, a fillet 32 is provided. At least for a short distancebelow the fillet 32 the punch has a diameter equal to, or 0.001 or 0.002inch larger than, the final, diameter of the pitch hole. In theoperation. of forcing the ball 25 through the pitch hole, downwardmovement of the punch is continued until the fillet 32 engages the edgeof the hole and chamfers it, as shown somewhat exaggeratedly at 3? inFig. 4. Such chamfering not only facilitates entry of the pin or bushinginto the pitch hole during subsequent assembly, but also tends toprevent the pin or bushing from tearing the side plate metal and thusdestroying the desirable surface conditions produced by the driftingoperation.

When the surfaces of the pitch holes are smoothed and made more dense asby drifting, and when nominal diameters and tolerances are establishedto insure minimum expelling forces such as previously set forth, we findthat fatigue resistance of the side plates will be increased by as muchas 50 We claim as our invention:

1. In a power-transmission chain, a series of pin links each comprisinga pair of side plates provided with alined holes and pin-s received insuch holes, the fit 0f the pins within the sideplate holes beingmaterially tighter than necessary to prevent movement of the pins in theside plates during operation of the chain, the holes 6 in the sideplates being enlarged to final size by drifting prior to assembly.

2. In a, power-transmission chain, a series of pin links each comprisinga pair of side plates provided with alined holes and pins received insuch holes, the fit of the pins within the sideplate holes being suchthat the force in pounds required to expel each pin from a side plate isat least 37,500 DT if the side plates are not heattreated and at least50,000 DT if the side plates are heat-treated, where D and T are,respectively, the diameter of the pins and the thickness of the sideplates in inches.

3. In a power-transmission chain, a series of pin links each comprisinga pair of side plates provided with alined holes and pins received insuch holes, the fit of the pins within. the sideplate holes being suchthat the force in pounds required to expel each pin from a side plate isat least 50,000 DT if the side plates are not heattreated and at least75,000 DT if the side plates are heat-treated, where D and T are,respectively, the diameter of the pins and the thickness of the sideplates in inches.

4. The invention set forth in claim 2 with the addition that the holesin the side plates are enlarged to final size by drifting prior toassembly.

5. The invention set forth in claim 2 with the addition that the holesin the side plates are enlarged to final size by drifting prior toassembly, that edge of each hole adjacent the longitudinal center lineof the chain being chamfered by cold compression.

6. In a power-transmission chain, a. series of pin links each comprisinga pair of side plates provided with alined holes and pins having a pressfit in such holes, the holes in the side plates are enlarged to finalsize by drifting prior to assembly, that edge of each hole adjacent thelongitudinal center line of the chain being chamfered by coldcompression.

7. In a power-transmission chain, a series of pin links each comprisinga pair of side plates provided with alined holes and pins having a pressfit in such hole, the holes in the side plates being enlarged to finalsize by drifting prior to assembly.

8. In a, power-transmission chain, a series of sprocket-engaging linkseach comprising a pair of side plates provided with alined holes andbushings received in such holes, the fit of the bushing within theside-plate holes being materially tighter than necessary to preventmovement of the bushings in the side plates during operation of thechain, the holes in the side plates being enlarged to final size bydrifting prior to assembly.

9. In a power-transmission chain, a series of sprocket-engaging linkseach comprising a pair of side plates provided with alined holes andbushings received in such holes, the fit of the bushings within theside-plate holes being such that the forcein pounds required to expeleach bushing from a side plate is at least 16,000 DT if the side platesare not heat-treated and at least 21,000 DT if the side plates areheat-treated, where D and T are, respectively, the diameter of thebushings and the thickness of the side plates in inches.

10. In a power-transmission chain, a series of sprocket-engaging linkseach comprising a pair of side plates provided with alined holes andbushings received in such holes, the fit of the bushings within theside-plate holes being such that the force in pounds required to expeleach bushing from a side plate is at least 21,000 DT if the side platesare not heat-treated and at least 32,000 DT if the side plates areheat-treated, wher D and T are, respectively, the diameter of thebushings and the thickness of the side plates in inches.

11. The invention set forth in claim 9 with the addition that the holesin the side plates are enlarged to final size by drifting prior toassembly.

12. The invention set forth in claim 9 with the addition that the holesin the side plates are enlarged to final size by drifting prior toassembly, that edge of each hole adjacent the longitudinal center lineof the chain being chamfered by cold compression.

13. In a power-transmission chain, a series of sprocket-engaging linkseach comprising a pair of side plates provided with alined holes andbushings having press-fit in such holes, the holes in the side platesare enlarged to final size by drifting prior to assembly, that edge ofeach hole adjacent the longitudinal center line of the chain beingchamfered by cOld compression.

14. In a power-transmission chain, a series of sprocket-engaging linkseach comprising a pair of side plates provided with alined holes andbushings having a press-fit in such holes, the holes in the side platesbeing enlarged to final size by drifting prior to assembly.

15. In a power-transmission chain, a plurality of sprocket-engaginglinks connected in series by pin links, each of said sprocket-engaginglinks comprising a pair of inner side plates provided with alined holesand bushings received in such holes, each of said pin links comprisingouter side plates provided with alined holes and pins received in saidholes and respectively extending through bushings in adjacentsprocket-engaging links, the fit of the bushings within the innerside-plate holes being such that the force in pounds required to expeleach bushing from a side plate is at least 16,000 U1 if the side platesare not heat-treated and at least 21,000 DT if the side plates areheat-treated, where D and T are, respectively, the diameter of thebushings and the thickness of the side plates in inches, and the fit of.the pins within the outer side-plate holes being such that the force inpounds required to expel each pin from a side plate is at least 37,500DT if the side plates are not heat-treated and at least 50,000 D'T' ifthe side plates are heattreated, where D and T are, respectively, thediameter of the pins and the thickness of the side plates in inches.

16. In the process of manufacturing powertransmission chain embodyingpin links each comprising side plates and a pair of pins, the steps ofpunching holes in the side plates, enlarging such holes to final size bydrifting, pressing the pins in the holes, and controlling the diametersof the respectively interfitting pins and holes so that the force inpounds required to expel any pin from a side plate is at least 37,500 DTif the side plates are not heat-treated and at least 50,000 DT if theside plates are heat-treated, where D and T are, respectively, thediameter of the pins and the thickness of the side plates in inches.

17. In the process of manufacturing powertransmission chain embodyingsprocket-engaging links each comprising side plates and a pair ofbushings, the steps of punching holes in the side plates, enlarging suchholes to final size by drifting, pressing the bushings in the holes, andcontrolling the diameters of the respectively interfi-tting bushings andholes so that the force in pounds required to expel any bushing from aside plate is at least 16,000 DT if the side plates are not heat-treatedand at least 21,000 DT if the side plates are heat-treated, where D andT are, respectively, the diameter of the bushings and the thickness ofthe side plates in inches.

18. In the process of manufacturing powertransmission chain embodyingpin links each comprising side plates and a pair of pins, the steps ofpunching holes in the side plates, pressing the pins in the holes, andcontrolling the diameters of the respectively interfitting pins andholes so that, the force in pounds required to expel any pin from a sideplate is at least 37,500 DT if the side plates are not heat-treated andat least 50,000 DT if the side plates are heat-treated, where D and Tare, respectively, the diameter of the pins and the thickness of theside plates in inches.

19. In the process of manufacturing powertransmission chain embodyingsprocket-engaging links'each comprising side plates and a pair'ofbushings, the steps of punching holes in the side plates, pressing thebushings in the holes, and controlling the diameters of the respectivelyinteriitting bushings and holes so that the force in pounds required toexpel any bushing from a side plate is at least 16,000 DT if the sideplates are not heat-treated and at least 21,000 DT if the side platesare heat-treated, where D and T are, respectively, the diameter of thebushings and the thickness of the side plates in inches.

20. Li a power-transmission chain, a series of links, each of said linkscomprising a pair of spaced side-plates overlapping the side plates ofan adjacent link, and means for interconnecting adjacent links, eachsaid means comprising a bushing and a pin extending through andprojecting beyond the ends of said bushing, the side plates of one ofthe associated links being provided with alined holes for receiving theends of said bushing and the side plates of the other of the associatedlinks being provided with alined holes for the reception pf the ends ofsaid pin, the fit of the pins within the pin-receiving sideplate holesbeing such that .the force in pounds required to expel each pin from aside plate is at least 37,500 DT if the side plates are not heattreatedand at least 50,000 U1 if the side plates are heat-treated, Where D andT are, respectively, the diameter of the pins and the thickness of theside plates in inches.

21. In a power-transmission chain, a series of links, each of said linkscomprising a pair of spaced side-plates overlapping the side plates ofan adjacent link, and means for interconnecting adjacent links, eachsaid means comprising a bushing and a. pin extending through andprojecting beyond the ends of said bushing, the side plates of one ofthe associated links being provided with alined holes for receiving theends of said bushing and the side plates of the other of the associatedlinks being provided with alined holes for the reception of the ends ofsaid pin, the fit of the bushings within the bushing-receivingside-plate holes being such that the force in pounds required to expeleach bushing from a side plate is at least 16,000 D'I if the side platesare not heat-treated and at least 21,000 DT if the side plates areheat-treated, where D and T are, respectively, the diameter of thebushings and the thickness of the side plates in inches.

22. In a power-transmission chain, a series of links, each of said linkscomprising a pair of spaced side-plates overlapping the side plates ofan adjacent link, and means for interconnecting adjacent links, eachsaid means comprising a bushing and a pin extending through andprojecting beyond the ends of said bushing, the side plates of one ofthe associated links being provided with alined holes for receiving theends of said bushing and the side plates of the other of the associatedlinks [being provided with alined holes for the reception of the ends ofsaid pin, each of said pins having a press-fit in the pinreceiving holesof the side plates, said pin-receiving holes lbeing enlarged to finalsize by drifting.

23. In a, power-transmission chain, a series of links, each of saidlinks comprising a. pair of spaced side-plates overlapping the sideplates of an adjacent link, and means for interconnecting adjacentlinks, each said means comprising a bushing and a pin extending throughand projecting beyond the ends of said bushing, the side plates of oneof the associated links being provided with alined holes for receivingthe ends of said bushing and the side plates of the other of theassociated links being provided with alined holes for th reception ofthe ends of said pin, each of said bushings having a press-fit in thebushing-receiving holes of the side plates, said bushing-receiving holesbeing enlarged to final size by drifting.

24. The invention set forth in claim 1 with the addition that that edgeof each hole adjacent the longitudinal center-line of the chain ischamfered by cold compression.

25. The invention set forth in claim 8 with the addition that that edgeof each hole adjacent the longitudinal center-line of the chain ischamfered by cold compression.

ARTHUR EL FOCKE. GEORGE G. MIZE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

